A variety of treatments are being explored to prevent or inhibit HIV infection, including vaccines and antiviral drugs. An additional modality for the treatment of HIV infection may be the use of bone marrow transplantation (BMT) to replace the HIV-infected lympho-hematopoietic cells with uninfected cells. In this context, it would be advantageous to be able to render the donor cells resistant to infection by HIV. It is our central hypothesis that retroviral vectors may be used to transduce anti- HIV ribozymes into human lympho-hematopoietic cells to inhibit subsequent HIV infection. Retroviral vectors are uniquely capable of transferring genes into primary cells such as hematopoietic stem cells and lymphocytes. We will design and construct retroviral vectors to transduce these cells with transcriptional units encoding anti-HIV ribozymes. Transfer and expression of the ribozymes will be studied using human lymphoid and myeloid cell lines, primary human bone marrow and T lymphocytes, and a murine BMT model. The ability of the expressed ribozymes to cleave HIV RNA will be assessed in three complementary systems: a) In vitro cleavage of HIV RNA, b) intracellular cleavage of a reporter transcript, and c) inhibition of HIV infection. We will also determine whether the expression of the ribozymes alters the development and function of the lympho- hematopoietic cells. In all, these studies will provide important new information about the potential for using a gene therapy approach with anti-HIV ribozymes to inhibit HIV infections.